The star formation and gas content of satellite galaxies around the Milky Way (MW) and Andromeda (M31) are depleted relative to more isolated galaxies in the Local Group (LG) at fixed stellar mass. We explore the environmental regulation of gas content and quenching of star formation in z = 0 galaxies at $M_{*}=10^{5\!-\!10}\, \rm {M}_{\odot }$ around 14 MW-mass hosts from the Feedback In Realistic Environments 2 (FIRE-2) simulations. Lower mass satellites ($M_{*}\lesssim 10^7\, \rm {M}_{\odot }$) are mostly quiescent and higher mass satellites ($M_{*}\gtrsim 10^8\, \rm {M}_{\odot }$) are mostly star forming, with intermediate-mass satellites ($M_{*}\approx 10^{7\!-\!8}\, \rm {M}_{\odot }$) split roughly equally between quiescent and star forming. Hosts with more gas in their circumgalactic medium have a higher quiescent fraction of massive satellites ($M_{*}=10^{8\!-\!9}\, \rm {M}_{\odot }$). We find no significant dependence on isolated versus paired (LG-like) host environments, and the quiescent fractions of satellites around MW-mass and Large Magellanic Cloud (LMC)-mass hosts from the FIRE-2 simulations are remarkably similar. Environmental effects that lead to quenching can also occur as pre-processing in low-mass groups prior to MW infall. Lower mass satellites typically quenched before MW infall as central galaxies or rapidly during infall into a low-mass group or a MW-mass galaxy. Most intermediate- to high-mass quiescent satellites have experienced ≥1–2 pericentre passages (≈2.5–5 Gyr) within a MW-mass halo. Most galaxies with $M_{*}\gtrsim 10^{6.5}\, \rm {M}_{\odot }$ did not quench before falling into a host, indicating a possible upper mass limit for isolated quenching. The simulations reproduce the average trend in the LG quiescent fraction across the full range of satellite stellar masses. Though the simulations are consistent with the Satellites Around Galactic Analogs (SAGA) survey’s quiescent fraction at $M_{*}\gtrsim 10^8\, \rm {M}_{\odot }$, they do not generally reproduce SAGA’s turnover at lower masses.
Characterizing the predicted environments of dwarf galaxies like the Large Magellanic Cloud (LMC) is becoming increasingly important as next-generation surveys push sensitivity limits into this low-mass regime at cosmological distances. We study the environmental effects of LMC-mass haloes (M200m ∼ 1011 M⊙) on their populations of satellites (M⋆ ≥ 104 M⊙) using a suite of zoom-in simulations from the Feedback In Realistic Environments (FIRE) project. Our simulations predict significant hot coronas with T ∼ 105 K and Mgas ∼ 109.5 M⊙. We identify signatures of environmental quenching in dwarf satellite galaxies, particularly for satellites with intermediate mass (M⋆ = 106–107 M⊙). The gas content of such objects indicates ram pressure as the likely quenching mechanism, sometimes aided by star formation feedback. Satellites of LMC-mass hosts replicate the stellar mass dependence of the quiescent fraction found in satellites of Milky Way-mass hosts (i.e. that the quiescent fraction increases as stellar mass decreases). Satellites of LMC-mass hosts have a wider variety of quenching times when compared to the strongly bimodal distribution of quenching times of nearby centrals. Finally, we identify significant tidal stellar structures around four of our six LMC analogues, suggesting that stellar streams may be common. These tidal features originated from satellites on close orbits, extend to ∼80 kpc from the central galaxy, and contain ∼106–107 M⊙ of stars.
more » « less- NSF-PAR ID:
- 10405226
- Publisher / Repository:
- Oxford University Press
- Date Published:
- Journal Name:
- Monthly Notices of the Royal Astronomical Society
- Volume:
- 513
- Issue:
- 2
- ISSN:
- 0035-8711
- Format(s):
- Medium: X Size: p. 2673-2688
- Size(s):
- ["p. 2673-2688"]
- Sponsoring Org:
- National Science Foundation
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ABSTRACT Low-mass galaxies are highly susceptible to environmental effects that can efficiently quench star formation. We explore the role of ram pressure in quenching low-mass galaxies ($M_{*}\sim 10^{5}{-}10^{9}\, \rm {M}_{\odot }$) within 2 Mpc of Milky Way (MW) hosts using the FIRE-2 simulations. Ram pressure is highly variable across different environments, within individual MW haloes, and for individual low-mass galaxies over time. The impulsiveness of ram pressure – the maximum ram pressure scaled to the integrated ram pressure prior to quenching – correlates with whether a galaxy is quiescent or star forming. The time-scale between maximum ram pressure and quenching is anticorrelated with impulsiveness, such that high impulsiveness corresponds to quenching time-scales <1 Gyr. Galaxies in low-mass groups ($M_\mathrm{*,host}10^{7}{-}10^{9}\, \rm {M}_{\odot }$) outside of MW haloes experience typical ram pressure only slightly lower than ram pressure on MW satellites, helping to explain effective quenching via group preprocessing. Ram pressure on MW satellites rises sharply with decreasing distance to the host, and, at a fixed physical distance, more recent pericentre passages are typically associated with higher ram pressure because of greater gas density in the inner host halo at late times. Furthermore, the ram pressure and gas density in the inner regions of Local Group-like paired host haloes are higher at small angles off the host galaxy disc compared to isolated hosts. The quiescent fraction of satellites within these low-latitude regions is also elevated in the simulations and observations, signaling possible anisotropic quenching via ram pressure around MW-mass hosts.
